The oxidizing agents present in bleaching agents are capable of lightening hair fiber by the oxidative breakdown of the hair's own pigment, melanin. For a moderate bleaching effect, the use of hydrogen peroxide as the sole oxidizing agent is sufficient, optionally with the use of ammonia or other alkalizing agents; a mixture of hydrogen peroxide and peroxydisulfate salts and/or peroxymonosulfate salts is typically used to achieve a greater bleaching effect.
For reasons of stability, commercial bleaching agents are customarily offered in two preparations packaged separate from one another, which are mixed immediately before use to form a finished application preparation. Commercial bleaching agents typically consist of a liquid oxidizing agent preparation and a powder including solid oxidizing agents. Alternatively, instead of the powder, pasty agents can be mixed with a liquid oxidizing agent preparation, as a result of which the problem of dust during the production and during mixing is prevented. Products with other components are also offered commercially.
Pasty bleaching agents usually include higher amounts of an inert oil, which can lead to stability problems (sedimentation of the solid oxidizing agents out of the oil). Even with peroxydisulfates that have not sedimented completely, a concentration gradient can occur within the packaging, so that different portions from the packaging after being mixed can produce a different lightening effect. A high viscosity is desirable to minimize these problems.
On the other hand, the viscosity of the bleaching paste must be so low that it can be mixed well and rapidly with the liquid oxidizing agent preparation. The resulting bleaching mixture must be sufficiently liquid, moreover, in order to the applied easily and uniformly, but viscous enough in order not to drip off the head or from application aids such as brushes. In addition, the resulting bleaching mixture should not separate, because sedimentation or phase separation is perceived by customers as a quality defect.
WO 2009/134875 A1 describes bleaching agents including persulfate salts and an oil gel, which in turn consists of oil(s) and specific polymers.
According to this invention, stability with respect to sedimentation and phase separation are cited as desirable properties of the agent.
EP 1 034 777 A1 discloses agents for lightening keratinic fibers, which include at least two preparations (A) and (B) packaged separate from one another, which are mixed immediately before use to form an application mixture, whereby preparations (A) are oil-based and include polymer(s), which form oelogels or lipogels.
The bleaching pastes disclosed in the state of the art are notable for low foaming of the application mixture. It has now been found that because of the rather large surface area of the application mixture, foaming can be quite desirable, because the product yield, spreadability of the application mixture, and the bleaching effect can be improved.
It is therefore desirable to improve further the properties of bleaching agents; in this case, on the one hand, the storage stability is to be increased, whereby not only the physical stability (sedimentation, phase separation) but also the chemical stability (decomposition of the persalts) are to be improved. Moreover, in particular the product yield, distributability of the application mixture, and the bleaching effect should be improved.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this